Portland clinker compositions

Agarwal et al. (A24) examined two alinite clinkers and further studied the process of their formation. The compositional range (Table 10.5) shows that, compared with typical Portland clinkers, they are of low LSF and low AR. The microstructures resembled those of typical Portland clinkers. XRD... 

Fig. 2.38 Liquidus curves at 1500°C in the part of the CaO-AljOj-SiO. Fields of CjS and CjA primary crystallization are denoted by dashed lines. Cj clinker composition (reduced to three oxides) and ash A (according to %% ). Alright side scheme of Heilmaim experiment ash-clinker sandwich Christensen N.H., Simonsen, Diffusion in Portland Cement Clinker , J. Am Ceram. Soc. 53, 361 (1970), published by John Wiley Sons Ltd, reproduced with the permission of Wiley Sons...

The clinker composition of the first group is a classic belite Portland cement. However, as it was proved experimentally in the case of raw materials, composed of chalk with high silica ratio, the high strength cements can be produced [130]. 

Binders that contain latently hydraulic or pozzolanic or non-reactive constituents in combination with Portland clinker (and usually also with calcium sulfate) are called composite or blended cements. 

The composition of Portland cement raw meals and Portland clinkers can be characterized by the mutual ratio of the main oxides present. The following ratios are those most widely employed (all amounts of oxides are given in wt%) ... 

The various constituents of Portland clinker differ in their grindability. In general, the grindability declines in the order calcimn sulfate>alite> almninate>ferrite>belite. As a consequence, different cement particle size fractions may vary in their phase composition. 

Chen, Y, and Odler, I. (1992b) The progress of Portland cement hydration effect of clinker composition, in Proceedings 9th ICCC, New Delhi, Vol. 4, pp. 24-30. 

Composite cements may be produced by grinding the mineral addition (or additions) together with Portland clinker and calcium sulfate, or by blending them with Portland cement produced separately. 

Composite cement—a cement that contains—in addition to Portland clinker and calcium sulfate—a latent hydranlic or pozzolanic constituent. Concrete—a material obtained by blending together an inorganic cement, water and concrete aggregate. 

ASTM C845 Type E-I (K) expansive cement manufactured ia the United States usually depends on aluminate and sulfate phases that result ia more ettriagite formation duriag hydration than ia normal Portland cements. Type K contains an anhydrous calcium sulfoaluminate, C A SI. This cement can be made either by iategraHy burning to produce the desired phase composition, or by intergrinding a special component with ordinary Portland cement clinkers and calcium sulfate. 

Calculate the overall Ca and Si contents (expressed as CaO and Si02) of a Portland cement clinker that has 55% alite, 30% belite, 5% alumi-nate phase, and 10% ferrite (assume ideal compositions for the latter two). Would you expect this to behave as a fast or a slow setting cement ... 

There are three fundamental stages in the process of manufacture of Portland cement, namely. (I) preparation of the raw mixture. (2) production of the clinker. (3) preparation of Ihe cement. Whether the process used is wet or dry. the raw materials are selected, analyzed, and mixed so dial, alter ireatmeni, Ihe product, or clinker, has a desired, narrowly specified composition A factory analysis of slurry, where the wet process is in use. is as follows calcium oxide 44%. aluminum oxide 3.5%. silicon oxide... 

Portland cement clinker potential phase composition is presented in Table 4. It could be seen that the C3A content in the clinker was 9.46% which is important for the cement hydration rate and cement sulfate resistance. Common Portland cement is not resistant to the sulfate influence because of the significant C3A content, whose hydrates react with sulfate ions resulting in expansive compounds. Portland cement with the higher resistance to sulfates must have low C3A content. Moderate to high content of mineral alite - C3S (54.72%) is usual for the Serbian cement plants and enables the addition of higher quantities of mineral admixtures without influencing the quality of final cement. 

Table 4 Potential phase composition of Portland cement clinker...

Alite is the most important constituent of all normal Portland cement clinkers, of which it constitutes 50-70%. It is tricalcium silicate (CajSiOj) modified in composition and crystal structure by incorporation of foreign ions, especially Mg ", AP and Fe. It reacts relatively quickly with water, and in normal Portland cements is the most important of the constituent phases for strength development at ages up to 28 days, it is by far the most important. 

The ferrite phase makes up 5 15% of normal Portland cement clinkers. It is tetracalcium aluminoferrile (CajAIFeOj) substantially modified in composition by variation in Al/Fe ratio and incorporation of foreign ions. The rale at which it reacts with water appears to be somewhat variable, perhaps due to differences in composition or other characteristics, but in general is high initially and intermediate between those of alite and belite at later ages. 

Table 1.2 Typical compositions of phases in Portland cement clinkers (weight per cent)... 

Table 1.3 Atomic ratios for phases in Portland cement clinkers, calculated from the typical compositions in Table 1.2... 

In many clinkers, the ferrite phase is closely mixed with aluminate due to a similarity in cell parameters, oriented intergrowth can occur (MIS). The close admixture often renders X-ray microanalysis difficult or unreliable. For ordinary Portland cement clinkers, the compositions found in dilferent laboratories are nevertheless remarkably consistent. Table 1.2 includes an average value based on the results of investigations using X-ray microanalysis (H8,K1,B2,U1,H3,B4) or chemical analysis of separated material (Yl). Table 1.3 includes suggested site occupancies corresponding to these data. 

A knowledge of the relevant high-temperature phase equilibria is necessary for understanding the factors that govern acceptable bulk compositions for Portland cement clinker, the conditions under which the latter can be manufactured, and the phase composition and microstructure of the resulting material. This chapter deals with these equilibria and with the phases to which they relate, with the exception of the major clinker phases, which were described in Chapter I. Some anhydrous phases primarily of interest in relation to other types of cement are also considered here. Principles underlying the preparation of anhydrous silicate, aluminate and other high-temperature phases are outlined. 

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